There are a large number of different types of processed food products such as frankfurters, bologna, salami, liverwurst, cheese rolls, turkey rolls, and the like manufactured throughout the world from a wide range of recipes and using many different types of processing conditions. A common feature of most categories of processed food products, particularly meat products, is that the mixture of ingredients of which the processed food product is prepared, commonly called an "emulsion," is stuffed into a casing. The food product can be processed while encased in the casing, and in many cases is then stored in the casing.
Casings most generally used are synthetic casings that may be of several different types and sizes depending on the category of food product to be prepared. In general, synthetic casings are supported or unsupported materials with the supported type, commonly called "fibrous food casing," utilized in the preparation of larger sizes of products such as bologna or turkey rolls. Fibrous casing consists of a fibrous web, usually a non-woven paper, formed into a seamless tube, impregnated with viscose which is regenerated in situ.
Since there are so many differences in recipes for making processed food products, such as sausages, and such different modes of processing the different products, it is difficult to provide a casing that is acceptable for all uses. For example, a category of sausages is typified by liver sausage which is moist, relatively soft, has a substantially high fat content and is cooked, usually in hot water or steam, by the manufacturer. In this type of sausage, moisture must be retained within the emulsion and the emulsion must be protected against oxidation which causes undesirable discoloration. A suitable casing should therefore be impermeable to moisture and have a low rate of oxygen transmission. Thus various casings having a suitable coating adhered to the surface thereof are commercially available for use in such applications. Food casings such as, for example, disclosed in U.S. Pat. No. 2,961,323, are coated with materials such as a polyvinylidine chloride copolymer which coating is substantially impermeable to moisture and has how oxygen and gas transmission characteristics.
Cellulosic food casings used in the sausage industry are multifunctional in that they can be used as containers during the processing of the product and as protective wrapping for the finished product. The casing is often removed from the sausage after processing and the sausage sliced and repacked into smaller units. When the casing is removed from the meat mass, there is frequently a tendency for some meat to adhere to the casing and be torn from the sausage with the casing, thereby causing surface marring of the sausage. The marring may range from minor scuffing to severe scarring depending upon the type of meat product and conditions of processing and peeling. Thus in the use of this type casing it may be advantageous to have an internally applied coating to the casing that will enable the casing to be easily removed from the meat mass encased therein.
In other applications it may be desirable to have a different type of coating applied to the inner surface of a fibrous casing. For example, in stuffing sausage emulsion containing a substantially high fat content into a cellulose hydrate casing, it may be desirable to have a vinylidene resin coating applied on the inner surface of the casing so that when the sausage emulsion is processed, the outer surface of the casing after being wet can dry and shrink thus encasing the sausage properly to provide a plump, attractively shaped product.
For other applications, it may be desirable to have the internal surface of a casing coated with a moisture proof layer of polyvinyl chloride, polyolefins and substituted polyolefins as well as vinyls, polyesters, nylons, and suitable copolymers of the above. There are many methods presently available for internally coating a tubing as, for example, the "slugging" technique described in U.S. Pat. No. 3,378,379. However, the primary disadvantage of applying a coating to the internal surface of a tubing is that it is very difficult to control the quality and quantity of the coating. Contrary to this, the knowledge available in the external coating art permits the use of various coating materials to be applied to the external surface of tubing under more regulated conditions so as to control the quality and quantity of the coating being applied. Accordingly, it is known in the art that coated flexible tubing, such as externally coated casings, can be turned inside out so as to position the coated surface on the interior of the tubing using devices as disclosed in U.S. Pat. Nos. 3,242,524 and 3,894,312.
It is the primary object of the present invention to provide a process for evaginating fibrous and cellulose tubing so as to reverse the inner and outer surfaces of said tubing.
Another object of the invention is to provide a process for easily turning fibrous or cellulosic tubing inside out without damaging such tubing.
Another object of the invention is to provide a process whereby coated fibrous or cellulosic tubing is humidified, shirred, and then turned inside out by drawing one end of the tubing through the bore of the shirred tubing out through the opposite end.